package com.hashTable;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class FourSum0131_18 {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>> res = new ArrayList<>();
        Arrays.sort(nums);
        if(target < nums[0] && nums[0] > 0) return res;

        for (int i = 0; i < nums.length - 3; i++) {
            if(i>0 && nums[i]== nums[i-1]) continue;

            for (int j = i+1; j < nums.length - 2; j++) {
                if (j>i+1 && nums[j] == nums[j-1]) continue;

                int left = j+1,right = nums.length-1;
                while (left < right){
                    long sum = nums[i] + nums[j] + nums[left] + nums[right];
                    if(sum == target){
                        res.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
                        while (left < right && nums[left] == nums[left+1]) left++;
                        while (left < right && nums[right] == nums[right-1]) right--;
                        left++;right--;
                    }else if(sum > target) right--;
                    else left++;
                }
            }
        }
        return res;
    }
}
